OpenGL "speed issue" with Quake2

I've been experimenting with gaming within a VBox guest since the support for Guest OpenGL has been added.

Unfortunately Quake 2 has some problems with VBox OpenGL. It's not that the OpenGL driver is too slow but there a inconsistent timing issues causing the game to be unplayable. Interestingly enough OpenGL itself seems to be very performant. Using the old 3Fingers demo
(crusher.dm2 and massive1.dm2) I get around 90 and 100 FPS which equals the performance I got back then with my PII-400 and 2x12 MB Voodoo2 in SLI mode.

I would call this bad. Since gtk-recordmydesktop is not fast enough to capture those speedissues I decided to capture a small video with my digicam. At first you'll see the two demos I mentioned and the fast rendering speed. Then I launch the first intro demo where you experience the slowdowns. At last I start a single player game where I guess the problem becomes obvious.